This invention relates generally to connecting devices, and more particularly to sequential connecting devices wherein a series of contacts are made sequentially as the connecting operation takes place.
It is well recognized in the art of electrical connections that in many cases when a device is being plugged into another device it is desirable to make a series of connections sequentially in a given preselected order. For example, when plugging a circuit card into a printed circuit board in many different types of computer devices it is necessary that the contacts be made and broken in a certain order. For example, in such situations it is often necessary to first make a ground connection, followed by a power connection and followed by a connection to signal lines, to assure that damage does not occur to the components or that the components work in a proper order and contain accurate data and information. This is especially critical in so called "hot plugging" applications where cards are attached and removed when the computer is running.
There have been several prior proposals for such type of connections. For example, U.S. Pat. No. 3,973,817, teaches a circuit board which has a plurality of contacts arrayed along the edge thereof with certain of the contacts extending farther out than other of the contacts; specifically, the ground contacts extend further out than the signal contacts so that there is in fact a plurality of spaced contact members extending along one edge which are of different lengths.
Similarly, U.S. Pat. No. 3,993,935, shows contacts at the edge of the circuit board located at various distances from the edge to allow sequential contact.
In another type of arrangement, U.S. Pat. No. 3,432,795, shows a plug and socket arrangement wherein the pins on the plug are formed to different lengths so that the insertion of the plug into the socket members is facilitated.
U.S. Pat. Nos. 3,829,814 and 3,289,149, show various ring, tip and sleeve type of connections of plugs and sockets. Other patents which show various types of contacts include U.S. Pat. Nos. 4,305,633; 4,079,440; 4,549,306; 4,734,041; 3,149,893; 3,399,372 and 3,871,729. Also U.K. Pat. No. 1,173,525 published December 10, 1969, discloses a sequential-type arrangement.
However, none of these patents provides a single plug connection where there is only a single pin or plug which make contact sequentially, and only with a given contact member in the plug.